A number of coin counting devices include sensors to discriminate coin denominations, discriminate coins from different countries, and/or discriminate coins from non-coin objects. These devices can include coin counters, gaming devices such as slot machines, vending machines, bus or subway “fare boxes,” etc. In such devices, accurate discrimination of deposited coins is important for economical operation of the device.
Some coin handling devices include electromagnetic sensors to discriminate deposited objects. Generally, these sensors generate an electromagnetic field that interacts with the object. The interactions are analyzed to determine whether the object is a coin, and if so, which denomination it is. Although these sensors can be extremely accurate, slight disparities in performance arise due to variations within the tolerances of fabrication that are inherent in the manufacturing process. These disparities can often be corrected for by calibrating the sensor prior to placing the device in service. However, the performance of the sensor can also be affected by ambient temperature variations in the operating environment. These temperature variations often necessitate manual calibrations of the sensor in order to maintain the highly accurate performance that is required of the device. Hence, conventional sensors often require periodic maintenance visits by technicians that increase the cost of operating these devices.